The company is accusing IBM of violating antitrust law by refusing to sell its z/OS operating system to clients who want to run the software on systems manufactured by T3. It also accuses IBM of harming competition by withholding patent licenses for its mainframe operating system and certain intellectual property.

The company has asked the EC to investigate IBM’s market price for its mainframe systems. It said that based on data from San Francisco-based IT consulting and market research firm Peerstone Research, European mainframe customers could have saved a total of $48 billion over 20 years if there had been fair competition in the market.

T3 introduced its IBM-compatible tServer mainframe line in 2000, using software from Fundamental Software that was based on an IBM patent license. In 2005, it signed an agreement with PSI that would enable the small mainframe manufacturer to create a more robust mainframe system, Liberty. But in 2006 IBM withdrew PSI’s and Fundamental Software’s license for its operating system and sued PSI for patent infringement.

In response to this, PSI and T3 filed a lawsuit against IBM in the US District Court of New York in 2007, accusing IBM of antitrust violations and unfair competition. However, in 2008 PSI withdrew the case after it was acquired by IBM.

T3 has the financial backing of Microsoft, which invested an undisclosed sum in the company last November to fund development of new products for mutual customers. The company has laid off 80% of its workforce in the US and Europe since 2006.

Steven Friedman, president of T3, said: Since November 2006, we have not been able to sell any of our hardware. No rational buyer would buy any hardware without software. The strategy that IBM implemented was successful – we’ve been decimated. The long-term harm is for EU customers because they have no other choice than IBM.